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From Andrei Ivanov <aiva...@iponweb.net>
Subject Re: Compaction Strategy guidance
Date Sun, 23 Nov 2014 09:53:40 GMT
Stephane,

We are having a somewhat similar C* load profile. Hence some comments
in addition Nikolai's answer.
1. Fallback to STCS - you can disable it actually
2. Based on our experience, if you have a lot of data per node, LCS
may work just fine. That is, till the moment you decide to join
another node - chances are that the newly added node will not be able
to compact what it gets from old nodes. In your case, if you switch
strategy the same thing may happen. This is all due to limitations
mentioned by Nikolai.

Andrei,


On Sun, Nov 23, 2014 at 8:51 AM, Servando Muñoz G. <smgesi@gmail.com> wrote:
> ABUSE
>
>
>
> YA NO QUIERO MAS MAILS SOY DE MEXICO
>
>
>
> De: Nikolai Grigoriev [mailto:ngrigoriev@gmail.com]
> Enviado el: sábado, 22 de noviembre de 2014 07:13 p. m.
> Para: user@cassandra.apache.org
> Asunto: Re: Compaction Strategy guidance
> Importancia: Alta
>
>
>
> Stephane,
>
> As everything good, LCS comes at certain price.
>
> LCS will put most load on you I/O system (if you use spindles - you may need
> to be careful about that) and on CPU. Also LCS (by default) may fall back to
> STCS if it is falling behind (which is very possible with heavy writing
> activity) and this will result in higher disk space usage. Also LCS has
> certain limitation I have discovered lately. Sometimes LCS may not be able
> to use all your node's resources (algorithm limitations) and this reduces
> the overall compaction throughput. This may happen if you have a large
> column family with lots of data per node. STCS won't have this limitation.
>
>
>
> By the way, the primary goal of LCS is to reduce the number of sstables C*
> has to look at to find your data. With LCS properly functioning this number
> will be most likely between something like 1 and 3 for most of the reads.
> But if you do few reads and not concerned about the latency today, most
> likely LCS may only save you some disk space.
>
>
>
> On Sat, Nov 22, 2014 at 6:25 PM, Stephane Legay <slegay@looplogic.com>
> wrote:
>
> Hi there,
>
>
>
> use case:
>
>
>
> - Heavy write app, few reads.
>
> - Lots of updates of rows / columns.
>
> - Current performance is fine, for both writes and reads..
>
> - Currently using SizedCompactionStrategy
>
>
>
> We're trying to limit the amount of storage used during compaction. Should
> we switch to LeveledCompactionStrategy?
>
>
>
> Thanks
>
>
>
>
> --
>
> Nikolai Grigoriev
> (514) 772-5178

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